(1) Field of the Invention
The present invention relates to microprocessors, particularly, a technique to reduce electric power consumption of microprocessors.
(2) Description of the Related Art
In the prior art, when an application program of a specific purpose is to be executed, it is known as a technique for reducing electric power consumption of a microprocessor to suspend an electric power supply (voltage impression) or a clock signal supply to one or more of independent functional blocks in the microprocessor that are not used in the execution of the application program.
For example, when a processor such as a VLIW (Very Long Instruction Word) microprocessor that includes a plurality of independent processing elements is installed in a product, and a specific application program is to be executed, it is possible to identify in advance, as a part of product designs, which processing elements will not be used in the execution of the specific application program, and to control and suspend the supply of clock signals to the unused processing elements. Through such control, it is possible to reduce electric power consumption of a microprocessor without degrading its processing performance. Further, a technique for controlling parallelism of a plurality of CPUs according to their system operation environment settings is disclosed in U.S. Pat. No. 5,913,068.
In recent years, many kinds of multi-functional information processing machines have been developed along with the multi-media-related technology being developed in the background.
Microprocessors installed in such multi-functional information processing machines are required to execute various kinds of application programs involving different types of data such as an application program focusing on control of graphical user interface or audio-visual digital signal processing, for example.
In general, each of such application programs includes calculation instructions specifying data calculation e.g. an addition, although types of data being treated are different from one application program to another. Generally speaking, all the calculation instructions in different application programs are processed in the same data calculation circuit in a microprocessor.
Accordingly, as for the data calculation circuit in a microprocessor, it is not possible to apply the technique of the prior art so as to control and suspend the supply of voltage impression and clock signals thereto, no matter which application program is to be executed.